This confuses me, can someone explain it?

The multiplicative property of equality states that for real numbers a, b, c, and d, if a = b and c = d, then ac = bd. true false

If a and −a are numbers on the number line, which expression must give the distance between them? a) 0 b) a c) |2a| d) |a|

Solve the equation: x - 9 = -6 + 5 a. 21 b. 7 c. 14 d. 2